고려대학교

초록/요약

The next-generation wireless networks are evolving toward an IP-based network that can provide various multimedia services seamlessly. To establish such a wireless mobile Internet, the registration domain supporting fast handoff is integrated with the DiffServ mechanism. However, in a DiffServ registration-domain environment, congestion control algorithms of TCP (Transmission Control Protocol) make the provision of an end-to-end QoS to TCP connections difficult because of TCP phase effect. Regarding the seamless mobile networking issue, there is a problem that performance of TCP can be severely degraded in Mobile IP-based wireless networks where packet loss not related to network congestion occurs frequently during inter-subnetwork handoff by user mobility. Since this packet loss by user mobility is not considered in TCP which was originally designed for the wired networks. To resolve such a problem in the networks using Mobile IP designed for supporting user mobility in the Internet, the packet buffering method recovering seamlessly the packets dropped due to user mobility has been proposed. The packet buffering method at a base station recovers those packets dropped during handoff by forwarding buffered packets at the old base station to the mobile users. But, when the mobile user moves to a congested base station in a new foreign subnetwork, those buffered packets forwarded by the old base station are dropped and TCP transmission performance of a mobile user in the congested base station degrades due to increased congestion by those forwarded burst packets. Moreover, when an AS (Assured Service) mobile user moves to a congested base station in a new foreign subnetwork, buffered packets of AS mobile user include both in-profile packets and out-of-profile packets. And the buffered out-of-profile packets dropped in a congested base station causes degradation of TCP transmission performance of an AS mobile user though buffered in-profile packets may not be dropped.